Blue Sky Marathon & Half: October 19, 2024

Registration 2024

  • Start: Blue Sky Trailhead, Horsetooth Mountain Park. Fort Collins, Colorado
  • Distance: 26.7 miles (3,500′) or 13.5 miles (1,500′)
  • Min/Max Elevation: 5,300′-6,500′ Marathon / 5,300′-5,700′ Half
  • Average Elevation: 5,700′ Marathon / 5,500′ Half
  • Terrain: Marathon: 22mi dirt singletrack, 3mi rocky singletrack, 2mi dirt road; Half Marathon: 11mi dirt singletrack, 1mi rocky singletrack, 1.5mi dirt road
  • Fauna: Deer, abert squirrel, golden eagle
  • Registration Cap: 375
  • Time Allowance: 9 hours Marathon / 8hr15min Half Marathon
  • Date: October 19, 2024

Taking place on the trails between Horsetooth Mountain Park and the Devil’s Backbone Open Space, the Blue Sky courses takes you on a north-south tour of the easternmost hogbacks of Northern Colorado’s Front Range mountains. With a moderate amount of elevation gain and loss and a variety of terrain, the route offers a little bit of something for everyone. It is designed to appeal to both veteran trail runners and those looking to experience their first trail racing adventure. The generous cut-offs should ensure a successful day for everyone.

The course is 100% dirt and 90% sweet Colorado singletrack. The terrain ranges in difficulty from smooth dirt trail to technical rock gardens. A small portion of the route is on dirt road (no motor vehicle access) and gravel trail, with the meat of the running done on the beautiful and distinctive redstone hardpack of the Blue Sky Trail.

After the race, kick back and enjoy the BBQ, awards and generous sponsor giveaways.



Current Entrant Lists

Fees for the 2024 Blue Sky Marathon & Half Marathon are as follows:

Dec 15 – Feb 29: $100
March 1– June 30: $110
July 1 – Oct 17: $120

Half Marathon
Dec 15 – Feb 29: $90
March 1– June 30: $100
July 1 – Oct 17: $110

What You Get in Return for Your Registration Fee:

  • A beautiful, challenging and well-marked course on some of the best trails in Fort Collins
  • Enthusiastic, knowledgeable race and aid station volunteers
  • Fully stocked aid stations
  • Larimer County Parks day parking pass
  • Generous Cut-Offs (Marathon: 9hrs / Half 8hr15min)
  • Gender specific race T-shirt
  • Unique finisher award and overall and age group awards
  • Post race BBQ and raffle
    • Vegetarian, vegan, gluten-free and non-alcoholic options are available as part of our standard race fare

Waiting List

In the event that the race sells out, we will maintain a waiting list and transfer runners from the waiting list to the race roster should other runners already registered not be able to attend.

Transfer Credit Policy

If you are not able to race, we will be able to offer a race transfer credit that can be applied to any future Gnar Runners race (valid for 12 months). Credit deadlines are as follows:

Until March 31: 100% credit of registration (excluding UltraSignup fees).
April 1 – July 31: 75% credit of registration (excluding UltraSignup fees).
August 1 – October 15: 50% credit of registration (excluding UltraSignup fees).

** In order to receive your credit, you must cancel your registration through the UltraSignup registration platform. You can cancel your registration by clicking the link at the bottom of your registration receipt or by logging into your UltraSignup account

The credit will be valid for one year from the event date, and will be tied to your account. It will apply automatically the next time you register for a Gnar Runners event.

Registered runners may also switch between race distances. Runners in the Half Marathon can pay the additional registration fee to upgrade to the Marathon. There is no charge for Marathon runners dropping down to the Half Marathon race. This process is self managed through your registration receipt and/or Ultrasignup account. The transfer deadline is Thursday (10/17) at midnight.

Cancellation & Refund Policy

Entries are non-refundable and non-transferable. In the event the race is cancelled due to extreme weather, fire, disease or for some other unforeseeable event, we cannot offer refunds or credits.

Course & Aid Stations

The Blue Sky HALF Marathon will be getting a course upgrade for 2024 to relieve congestion on the trails! Expect a bit more vertical gain than 2023 as we tour Horsetooth Mountain Park. All marathon course details are unchanged.
Updated 5/15/24 – Here’s the new course on Strava, and we’ll get all the rest of the info updated ASAP.

Course Map

Interactive Map

Course GPX Files

Elevation Profiles

Blue Sky Trail Marathon Elevation Profile

Marathon Aid Stations


Aid Station Mile Split Total Gain Descent Cut-Off Drop Bag Aid
Towers 4.4 4.4 1150 150 No Fluids Only
Blue Sky (Start/Finish) 4.8 9.2 150 1150 10:00a Yes FULL
Indian Summer North 1 4.0 13.2 450 350 No FULL
Indian Summer South 1 2.4 15.6 300 400 12:30p No FULL
Hunter Turnaround 2.3 17.9 400 250 No Safety Only
Indian Summer South 2 2.4 20.3 250 400 1:45p No FULL
Indian Summer North 2 2.4 22.7 400 300 No FULL
Finish 4.0 26.7 350 450 4:00p Yes FULL

With the exception of the Towers Aid at marathon mile 4.4, all aid stations will be fully stocked and staffed with volunteers. The Towers aid station will be staffed with volunteers but offer fluids & gel only.

All other aid stations will offer Gnarly Nutrition Fuel2O sports drink, water and soda plus a variety salty and sweet bites, and a selection of fruit.

***There will be GF/Vegan alternatives for nearly all non-GF/V standard offerings. These are typically held back to save them for those who need them, so please ASK! Also note that while we will do our best to keep utensils and trays separated for these as well as common allergens, this is the backcountry and cross-contamination can occur.

While we will provide plenty of electrolyte options in drink mix and salty real foods, we deem the risks associated with salt in concentrated pill form to be more than we’re comfortable providing. We won’t restrict runners from using their own salt caps, but will not have them available at aid stations.

Time Cut-Offs

Marathon course cut-offs will be enforced at the following aid stations:

  • Blue Sky Aid Station (mile 9.2) at 10:00am. 3:00 total time.
  • Indian Summer South outbound (mile 15.6) at 12:30pm. 5:30 total time.
  • Indian Summer South inbound (mile 20.3) at 1:45pm. 6:45 total time.

There are no on-course cut-offs for the half marathon.

Drop Bags

Marathon runners may leave a drop bag at the Blue Sky Start/Finish to pick up at mile 9.2. We will have a tarp to set bags out next to the aid table. Pack your gear to stay dry in case we get any rain.

Drop bags should be clearly labeled with your name and bib number. Please keep your drop bag to a reasonable size (small duffel bag or stuff sack). Please do not leave any valuable items in your drop bags – volunteers are not responsible for lost items. Drop bags will not be transported to any other locations on course.

Course Marking

The courses will be well marked with pink flagging and pink pin flags. Important intersections will be supplemented with flour ground markings and directional arrows. On longer stretches of trail without intersections, confidence flagging will be placed approximately every quarter mile. Turns will be marked heavily.


There will be ample facilities at the start/finish. In addition, there are park facilities that can be used in the campsite between the main Marina parking area and the start. These facilities will also be passed at marathon mile 1-2 and 8-9. We will have an additional portable toilet at the Indian Summer South Aid.

Crewing & Spectating

Runners are not allowed to receive assistance from crew on the course outside of the Blue Sky Start/Finish area at mile 9.2. No pacing is permitted.

Much of the course is run on trails that are not easily accessible to spectators, especially for the half marathon. The best viewing points are the Start/Finish line at the Blue Sky Trailhead (also marathon mile 9.2 Aid), the Soderberg Trailhead, and the Hunter Loop 18-mile turnaround.

NO Crewing is allowed at the Indian Summer North or South Aid Stations.

  • For the Start/Finish, park in the Marina parking area (see above) and walk over, please do not drive through or park at the start/finish.
  • To access the Soderberg Trailhead, from the Start/Finish, turn north on Shoreline Drive and make a left into the trailhead parking lot. If the parking lot is full, you may park in the Marina parking area and walk north through the campground to the trailhead.
  • To access the Hunter loop (18-mile turn), drive to the Devil’s Backbone Trailhead near Loveland. Take Highway 34 West from Loveland and take a right onto Hidden Valley Rd and follow signs to the Devil’s Backbone parking lot. Follow the trail north up the hill to the junction of the Wild and Hunter loops (roughly 2 miles).

The entire trail system is open to the public if you would like to spectate and encourage your runner elsewhere on course; however, crewing and pacing by foot or by bike is not allowed and will result in the disqualification of your runner.


There will likely be organized training runs on Saturdays in September/October for Blue Sky. See the Fort Collins Trail Runners Facebook Group for group run postings, as well as our Community Page for suggested routes.

Detailed Marathon Course Directions

Start to Towers Aid (4.4mi): The start line is located at the Blue Sky Trailhead off County Road 38E, six miles west of Fort Collins. From the start, you will run north on the Blue Sky Trail through the campground 1.3 miles to the Soderberg Trailhead, continuing north on the Swan Johnson Trail to Towers Rd where you will take a left up the hill to Towers Aid.

Towers Aid to Blue Sky Aid (9.2mi): Volunteers at Towers Aid will direct you out of the aid station to turn right onto the Herrington Trail. Shortly after the turn onto Herrington you will bear left onto the Stout Trail. The descent down the Stout Trail is rocky, so watch your footing, though be sure to check out the reservoir views. Stout will contour around the hillside to bring you back to Towers Rd. Turn right on Towers Rd and take another right back onto Swan Johnson south back to the Soderberg Trailhead. Continue south back through the campground to the Blue Sky Aid start/finish area.

Blue Sky Aid to Indian Summer North Aid (13.2mi): Continue south on the Blue Sky Trail. This section of the trail will be winding, rolling single track with many blind corners. Please be aware that the trail is open for public use. You will pass only one trail junction with the Rim Rock Trail. Continue straight past this intersection down the hill into the valley towards Indian Summer North Aid, which will be visible from this point on the course.

Indian Summer North Aid to Indian Summer South Aid (15.6mi): The Indian Summer North Aid is at the junction of the Indian Summer Loop. Make sure that your number is recorded at the aid station and volunteers will direct you to turn right up the hill onto the Indian Summer Trail. On completing the loop, make a right at the trail junction to turn south back onto the Blue Sky Trail. Indian Summer South Aid will be located about a quarter mile south of this intersection. This is your last chance for aid before a long and difficult 5 mile section through the Devil’s Backbone side of the course. Make sure you leave with adequate water.

Indian Summer South Aid to Hunter Turnaround to Indian Summer South Aid (20.3mi): Continue south on the Blue Sky Trail. Once you pop over the hogback cliff band, the terrain becomes very rocky and technical. There are two loops to negotiate here and all you need to remember is to turn right. There is only one right way to go. At the first junction with the Laughing Horse Loop, turn right. At the end of the Laughing Horse Loop, continue straight ahead. At the second junction with the Hunter Loop, turn right. At the end of the Hunter Loop, a course marshal will record your number. Volunteers hike into this location so there will be no aid available. The course marshal will direct you to continue around the Hunter Loop, and you will return north towards the finish. On the return trip at the end of the Hunter Loop, turn right and continue north. At the next Laughing Horse Loop junction, turn right. At the end of the Laughing Horse Loop continue straight north, back down off the ridge into the valley to Indian Summer South Aid.

Indian Summer South Aid to Indian Summer North Aid (22.7mi): From Indian Summer South Aid, you will return the way you came. About a quarter mile north of the aid station, you will turn left to go back up and over the Indian Summer Loop to Indian Summer North Aid.

Indian Summer North Aid to Finish (26.7mi): After leaving Indian Summer North Aid, you’ll have a short climb up past the Rim Rock junction. From there you’ll have just a few more miles of rolling single track to the finish.

Race Rules

Race rules are designed to provide a safe and fair experience for everyone involved and to help ensure our ability to produce the race again next year. Major rule infractions by racers will result in immediate disqualification of the racer. Please do not argue with or harass our volunteers. Please direct any questions and feedback to us here.

  1. The marathon will be limited to 9 hours and the half marathon will be limited to 8hr15min. Both will end at 4:00pm. Please refer to the Aid Station section of this page for intermediate cut-offs.
  2. At each aid station, volunteers will record runner bib numbers. Runners are responsible for making sure that aid station volunteers record their number. Please make sure that your bib number is visible from the front and call out and confirm your number when passing through an aid station. This is important so that we can keep track of runners, record your intermediate race splits and know that you are not lost or injured.
  3. If you need to drop out of the race for any reason, you must check out with the nearest aid station or course volunteer.
  4. Purposeful littering is prohibited and will result in an immediate disqualification.
  5. Stay on the trail. No bushwhacking or short cutting. In case of wet trail conditions, please run through any muddy sections to avoid widening the trail. Yield to pedestrian and horses. Mountain bikers should yield to runners, but please use common sense in all circumstances.
  6. Pacers are not allowed. Crewing is allowed at designated aid stations only.
  7. No mechanical aid (poles, traction devices, etc.) unless approved by race staff prior to the race for a specific reason.
  8. All runners should carry a 16oz minimum water bottle or bladder that can be refilled at aid stations. There will be no water cups at aid stations.
  9. Dogs are not allowed on the course with runners.


Friday 10/18:

4:00-7:00p: Optional packet pick-up at Altitude Running 2531 S Shields St #2N, Fort Collins, CO 80526

Saturday 10/19:

5:30-6:45a: Race Day Packet Pickup
6:50a: Marathon Pre-Race Briefing
7:00a: Marathon Start
7:35a: Half Marathon Pre-Race Briefing
7:45a: Half Marathon Start
9:30a-4:00p: Finish Line BBQ
10:00a: Blue Sky Aid Cut-Off – Marathon
10:15a & Beyond: Half Marathon Awards & Raffle
12:30p: Indian Summer South Aid Southbound Marathon Cut-Off
1:30p & Beyond: Marathon Awards & Raffle
1:45p: Indian Summer South Aid Northbound Marathon Cut-Off
4:00p: Finish Cut-Off

Parking & Directions

The Start/Finish line is located at the Blue Sky Trailhead off of County Road 38E across from the Canyon Bar & Grill.

All vehicles containing registered runners will receive a park pass – good for one vehicle – as part of their entry fee. Any other vehicles (crews/spectators) will be required to have a Larimer County Parks Annual Pass or purchase a day pass on-site for $10.

Parking for all participants and spectators will be located in the Inlet Bay Marina parking lot off of Shoreline Drive. It is a 0.7mi walk from the Marina to the start/finish area. Carpools of two or more runners will be given priority parking at the Blue Sky Trailhead at the start/finish until it fills. Please carpool if you can and want priority parking.

Parking is in designated parking spaces only. There is no parking allowed in the campground areas (unless you have reserved and paid for a nearby campsite.)

Runner/Spectator Drop Off

Drop offs can be made at the small turn out off Shoreline Drive just around the corner from the Blue Sky Trailhead. Vehicles should not stop anywhere on the side of 38E.

**Parking is not allowed anywhere on 38E, along Shoreline Drive, or on any connecting residential street.**

Driving Directions

4780 W County Road 38E, Fort Collins, Colorado, 80526